Polycentricity at its boundaries: consistent or ambiguous?

Polycentricity describes a certain region by the relationship of a selection of its most central spatial entities. We identify two sources of shortcomings in measures of polycentricity: the delineation of the region under study and the number of units considered within it. Both bear the risk of manufacturing polycentricity before measuring it, the first by setting borders between regions, the latter by distinguishing 'central' and 'peripheral.' Building on a literature review, which traces these challenges in debates on polycentricity, we empirically investigate their impact for two German cases. The study utilizes rank-size analysis based on employment (morphological) and commuting (functional), to assess polycentricity and compare it over cases and dimensions. By varying scales and units considered, we extend the regular scope of analysis and uncover differences strengthening an interpretation of polycentricity as an ambiguous concept. This challenges descriptions and comparisons resting on clear-cut borders and 'center' definitions. [ABSTRACT FROM AUTHOR]